The UCLA Pediatric Epilepsy Surgery Research Program incorporates established clinical and basic science groups from Pediatric Neurology, Neurosurgery, the Mental Retardation Research Center, Neuropathology, Neuropsychology, Psychiatry and Linguistics into a cohesive group for the study of the clinical and developmental features of cortical resection for the treatment of epilepsy and uses the tissue thus removed to study the pathologic and electrophysiologic properties of the tissue. Young children with "catastrophic" epilepsy have a poor prognosis for development if the seizures are not controlled. Currently available medical therapies are often not successful in controlling seizures but surgery to remove an epileptic focus offers hope for some of these children. Our recent experience indicates that surgical "cure" is possible in some children with generalized seizure disorders (i.e. infantile spasms) as well as catastrophic focal seizure disorders (i.e. infantile hemiplegic epilepsy). However, studies are needed to determine the best applications. Project #1 will prospectively study 30 children in a randomized clinical trial to determine outcome of cortical resection for the control of medically intractable infantile spasms. Project #2 will study language development in the surgical subjects. Four studies will be conducted regarding the neurological basis of language acquisition and hemispheric specialization for language. There are 3 basis science projects utilizing the tissue taken at surgery. Project #3 will study intrinsic electrophysiological properties of cortical neurons. Project #4 will study the ability of neuromodulators to effect the electrophysiological responses. Project #5 will study the structure and biochemistry of human epileptic tissue and the development of the cortex.